In continuous casting, a billet is cast from liquid metal using a casting die. The billet is drawn from the casting die with a solidified investment and a liquid core. A significant factor for a good quality billet is keeping the casting level, i.e. the liquid metal level in the casting die, constant. The casting level can be regulated. Designing the regulator for the casting level is difficult because the parameters of the controlled system, i.e. the casting apparatus and the casting die, are subject to great variations, to a certain extent. In addition, the design of the regulator for the casting level is further complicated because disturbance variables act on the casting level. In continuous casting, the billet leaves the casting die while it is still soft. The billet is guided on support rollers in a take-up device. Bulging of the billet occurs between the support rollers that has an effect on the casting level in the casting die.